This invention relates to a novel and useful copolyamide, in particular, an alcohol-soluble copolyamide having improved properties.
Generally, polyamides are difficult to dissolve in organic solvents. Only a few solvents such as phenol, formic acid and sulfuric acid can dissolve the usual polyamides.
In recent years, applications of polyamide solutions as adhesives, coating agents, casting films and so on have been developed on an industrial scale.
A polyamide which is soluble in lower alcohols, or mixtures of such alcohols with hydrocarbons, is usually used as the polyamide for these applications.
As a typical polyamide used for these applications, a copolyamide obtained by polymerizing a monomer mixture comprising .epsilon.-caprolactam, hexamethylene diammonium adipate, and hexamethylenediammonium sebacate (so-called nylon 6/66/610) has been already proposed.
It has been found that this conventional copolyamide has serious disadvantages when it is used as an alcohol solution. Specifically, this conventional copolyamide is lacking in solution stability.
Generally, the polyamide is subjected to practical use as a 10-30 percent methanol solution. When such a methanol solution is stored at ambient temperature, the copolyamide precipitates from the solution, or the whole solution coagulates into a gel, and these difficulties are not avoidable.
The conventional copolyamide solution usually coagulates into a gel after one to three days storage. Therefore, it is necessary to prepare the solution in the quantity required for each usage at the time, or it is necessary to perform the troublesome step of re-dissolving the gelated solution by heating.
On the other hand, when the copolyamide solution is to be used as a coating agent for printed paper, for example, the resulting coating film is required to have good transparency. The conventional copolyamide does not provide a coating film having satisfactory transparency.
Accordingly, an object of this invention is to provide a novel and useful alcohol-soluble copolyamide having superior solution stability and good transparency.